[Patent document 1] JP 2000-513296 A (U.S. Pat. No. 6,227,501 B1)
An ultrasonic sensor apparatus will be explained which measures a distance from a vehicle to an obstacle using ultrasonic waves as an example of a distance sensor apparatus. A recent vehicle may be equipped with a clearance sonar that is an obstacle detector to assist a driving manipulation at parking, for example. The clearance sonar includes the predetermined number of ultrasonic sensor apparatuses, e.g., two of which are disposed in the front bumper and four of which are disposed in the rear bumper. The clearance sonar detects a time duration until when ultrasonic waves transmitted from the ultrasonic sensors hit an obstacle and return, thereby measuring a distance from the vehicle to the obstacle. When the distance becomes smaller than a setup value, a driver may be notified via a sound. The above ultrasonic sensor apparatus is described in Patent document 1.
As illustrated in FIG. 13, an ultrasonic sensor apparatus 3′ is divided into two parts of a bezel 43′ and a case body 46′ when attaching to an attachment hole 54 of a bumper 2; after placing oppositely the two parts on the outside and the inside of the bumper 2, the two parts are brought close to each other and attached to the bumper as one assembly.
In a conventional ultrasonic sensor apparatus 3′, several metal springs 55′ are attached to the bezel 43′ that supports a sensor unit 42′; the metal springs 55′ are engaged at circumference edge portions of the attachment hole 54 in the bumper 2, achieving the fixation of the ultrasonic sensor apparatus 3′. The metal springs 55′ are manufactured independently from the bezel 43′, for example, by using a multi-forming die, and are thereafter attached with the bezel 43′ to be one assembly. Therefore, the process is needed for attaching the metal springs 55′ to the bezel 43′, increasing costs of the ultrasonic sensor apparatus 3′.
Further, the conventional ultrasonic sensor apparatus 3′ uses an attachment operation having two actions of the first action for attaching previously the bezel 43′ to the bumper 2, and the second action for attaching the case body 46′. Another attachment operation may be considered which attaches first the bezel 43′ and the case body 46′, and inserts them to the attachment hole 54 of the bumper 2. In such an attachment operation, when passing through the attachment hole 54, the metal springs 55′ are plastically deformed to be crushed. This may cause a possibility not to sandwich the bumper 2. Further, it is also difficult to respond to bumpers 2 having different thicknesses, respectively.